[archiso] Split README file

Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>

docs/README.build

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+INDEX
+-----
+
+* Build requirements
+* Image types generated by mkarchiso.
+* File format for aitab.
+* Why the /isolinux and /arch/boot/syslinux directories?
+* Building the most basic Arch Linux live media. (configs/baseline)
+* Building official Arch Linux live media. (configs/releng)
+
+
+
+*** Build requirements
+
+** For mkarchiso script needs these packages (build host):
+ + squashfs-tools          for mksquashfs
+ + libisoburn              for xorriso
+ + btrfs-progs             for mkfs.btrfs (optional)
+
+** For configs/releng build.sh needs theses packages (build host):
+ + dosfstools              for mkfs.vfat
+ + patch                   for patch
+ + lynx                    for fetching the latest installation guide
+
+** For these hooks needs these packages (on target root-image)
+* archiso
+ + (none)
+* archiso_loop_mnt
+ + (none)
+* archiso_pxe_common
+ + mkinitcpio-nfs-utils    for ipconfig
+* archiso_pxe_nbd
+ + nbd                     for nbd-client
+* archiso_pxe_http
+ + curl                    for curl
+* archiso_pxe_nfs
+ + mkinitcpio-nfs-utils    for nfsmount
+* archiso_shutdown
+ + (none)
+
+
+*** Image types generated by mkarchiso.
+
+* image-name.sfs     SquashFS image with all files directly on it.
+* image-name.fs.sfs  SquashFS with only one file inside (image-name.fs),
+                     which is an image of some type of filesystem
+                     (ext4, ext3, ext2, xfs), all files reside on it.
+
+
+*** File format for aitab.
+
+The aitab file holds information about the filesystems images that must be
+created by mkarchiso and mounted at initramfs stage from the archiso hook.
+It consists of some fields which define the behaviour of images.
+
+# <img>         <mnt>                 <arch>   <sfs_comp>  <fs_type>  <fs_size>
+
+<img>      Image name without extension (.fs .fs.sfs .sfs).
+<mnt>      Mount point.
+<arch>     Architecture { i686 | x86_64 | any }.
+<sfs_comp> SquashFS compression type { gzip | lzo | xz }.
+<fs_type>  Set the filesystem type of the image
+           { ext4 | ext3 | ext2 | xfs | btrfs }.
+           A special value of "none" denotes no usage of a filesystem.
+           In that case all files are pushed directly to SquashFS filesystem.
+<fs_size>  An absolute value of file system image size in MiB.
+           (example: 100, 1000, 4096, etc)
+           A relative value of file system free space [in percent].
+           {1%..99%} (example 50%, 10%, 7%).
+           This is an estimation, and calculated in a simple way.
+           Space used + 10% (estimated for metadata overhead) + desired %
+
+
+*** Why the /isolinux and /arch/boot/syslinux directories?
+
+The /isolinux directory holds files needed for the ISOLINUX boot loader
+module of SYSLINUX. ISOLINUX can not find config files on
+/arch/boot/syslinux, like other boot loaders modules (EXTLINUX, SYSLINUX, etc).
+When make your custom boot-pendrive, you need to copy /arch directory to it.
+/isolinux/isolinux.cfg just holds /arch/boot/syslinux/syslinux.cfg
+
+
+
+*** Building the most basic Arch Linux live media. (configs/baseline)
+
+* Install needed packages.
+  # pacman -S git make squashfs-tools libisoburn rsync --needed
+
+* Install archiso.
+  # git clone git://projects.archlinux.org/archiso.git
+  # make -C archiso install
+
+* Build a basic iso.
+  # /usr/share/archiso/configs/baseline/build.sh
+
+Note: If you want to customize, just see the configs/releng directory which is
+used to build official images with much more things.
+
+
+*** Building official Arch Linux live media. (configs/releng)
+
+* Install needed packages.
+  # pacman -S git make squashfs-tools libisoburn dosfstools lynx patch --needed
+
+* Install archiso.
+  # git clone git://projects.archlinux.org/archiso.git
+  # make -C archiso install
+
+* Build them!
+  # /usr/share/archiso/configs/releng/build.sh build all
+
+Note: See build.sh -h for more options.